Conventional optical disks, such as CD and DVD, adopt the column data system which ties 1-bit information to a line and records it on a plane surface by a piece of laser pulse, and blue laser light DVD provides a storage capacity of several gigabytes per disk. On the other hand, holographic data recording system records thousands of bits page information in volume by a piece of laser pulse, and research progresses to the objective to attain several terabytes per disk. Electronic holography system calculates hologram interference fringe formed by the interference of coherent light, images the interference fringe pattern on a display device by the electronic control, and displays natural three-dimensional image by the display device. Along with the development of the display device that can build more high-definition system, the research and development of three-dimensional moving picture utilizing holography technology progresses, however, very big space-bandwidth product is required to the device for imaging fine interference fringe pattern of hologram.
Hologram is divided into an amplitude modulation type and a phase modulation type, the transmittance and diffraction efficiency of the phase modulation type hologram are higher than those of the amplitude modulation type hologram. Spatial light modulators that modulate optical phase, switches the frame of millions of pixels 10,000 times or more per second, may be useful for applications, such as the hologram data storage that modulates digital information into optical phase plane, records and reproduces the information by the optical hologram.
In the method modulating optical phase by controlling the position of light reflection surface, a micro-electromechanical device of micron-size structure has ability to set the position of light reflection surface with the accuracy sufficiently shorter than a wavelength of light. However, in driving micro-electromechanical device, it may be difficult to assure a reproducibility of the accuracy by some factors, such as the drive method like an analog drive, process variation at the time of manufacture, change on physical property of structural material by temperature, and metal fatigue by long-term-reliability operation.
The objectives of this invention are to provide a type of the micro-electromechanical device that modulates an optical phase by the control of the position of light reflection surface with high accuracy, at high speed, and in high resolution.